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Frans_M_Everaerts_Isotachophoresis_378342.pdf

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GENERAL EQUATIONS 41<br />

i<br />

Similar equations can be derived for all ionic species in all zones.<br />

Combining eqns. 4.7 and 4.9, the ionic concentration c u, zAr-i, can be expressed<br />

Ar,<br />

as the total concentration of A,.:<br />

c~R, V,zA -<br />

R<br />

This equation wil be used in the following sections<br />

4.2.2. Electroneutrality equations<br />

(4.10)<br />

(4.1 1)<br />

In accordance with the principle of electroneutrality, the arithmetic sum of all<br />

products of the concentrations of all forms for all ionic species and the corresponding<br />

valences, present in each zone, must be zero. While the first zone contains one ionic species<br />

of the sample, each following zone always contains one ionic species more, viz., that<br />

ionic species with the highest effective mobifity of the ionic species that remain. The<br />

Uih zone will consequently contain Uionic species of the sample. For one ionic species,<br />

the sum of all products of the concentrations and the corresponding valences for the<br />

different ionic forms is<br />

(4.12)<br />

This is the total amount of charge present per volume for this ionic species. If the ionic<br />

species are numbered in order of decreasing effective mobilities, for the Uth zone we can<br />

write as ‘electroneutrality equation’:<br />

[ 2 U<br />

CH,rJ-COH, U+ 2 [(‘Ar-’) ‘Ar,U,zAr-i]) +~~(‘B-‘) ‘B,U, zg-i] = (4.13)<br />

r= 1

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